From 6b22a048fc1726d8516b68cdd54853c32b4725d7 Mon Sep 17 00:00:00 2001
From: Dmitry Medvedev <dmitri.medv15@gmail.com>
Date: Mon, 22 Jun 2026 01:45:15 +0500
Subject: [PATCH] added Mater VIEW for Pet Project 'lesson_popularity_ranking'

---
 ... Pet project Lesson_popularity_ranking.sql | 64 +++++++++++++++++++
 1 file changed, 64 insertions(+)
 create mode 100644 dmedvedev/11.5 Pet project Lesson_popularity_ranking.sql

diff --git a/dmedvedev/11.5 Pet project Lesson_popularity_ranking.sql b/dmedvedev/11.5 Pet project Lesson_popularity_ranking.sql
new file mode 100644
index 0000000..a2bb0da
--- /dev/null
+++ b/dmedvedev/11.5 Pet project Lesson_popularity_ranking.sql	
@@ -0,0 +1,64 @@
+CREATE MATERIALIZED VIEW lesson_popularity_ranking AS 
+
+SELECT 
+	pl.id AS lesson_id,
+	pl.title AS lesson_title,
+	pc.id AS course_id,
+	pc.title AS course_title,
+	total_views_lesson.total_views AS total_views,
+	table_unique_viewers.unique_v AS unique_viewers,
+	ROUND(AVG(views_one_user_per_one_lesson.views_per_viewer), 2) AS avg_views_per_viewer, --также это можно было посчитать total_views/unique_viewers
+	DENSE_RANK() OVER (
+		ORDER BY total_views_lesson.total_views DESC NULLS LAST
+	) AS popularity_rank,
+	
+	ROUND(table_unique_viewers.unique_v * 100.0 / table_enrolled_users.enrolled_to_course, 2) || '%' AS completion_rate
+	
+	FROM pet_lessons pl
+
+	LEFT JOIN (
+		SELECT 
+			lesson_id,
+			COUNT(*) AS total_views
+		FROM pet_lesson_views
+		GROUP BY lesson_id
+	) AS total_views_lesson
+		ON total_views_lesson.lesson_id = pl.id
+	
+	LEFT JOIN pet_courses pc
+		ON pc.id = pl.course_id
+	
+	LEFT JOIN (
+		SELECT
+			lesson_id,
+			COUNT(DISTINCT user_id) AS unique_v
+		FROM pet_lesson_views plv
+		GROUP BY plv.lesson_id
+	) AS table_unique_viewers
+		ON table_unique_viewers.lesson_id = pl.id
+	
+	LEFT JOIN (
+		SELECT
+			lesson_id,
+			user_id,
+			COUNT(*) AS views_per_viewer
+		FROM pet_lesson_views plv
+		GROUP BY user_id, lesson_id
+		ORDER BY user_id, lesson_id
+	) AS views_one_user_per_one_lesson
+		ON views_one_user_per_one_lesson.lesson_id = pl.id
+	
+	LEFT JOIN (
+		SELECT
+			course_id,
+			COUNT(DISTINCT user_id) AS enrolled_to_course
+		FROM pet_enrollments pe
+		GROUP BY course_id
+	) AS table_enrolled_users
+		ON table_enrolled_users.course_id = pc.id
+	
+		
+		
+	GROUP BY pl.id, pl.title, pc.id, pc.title, total_views_lesson.total_views, table_unique_viewers.unique_v, table_enrolled_users.enrolled_to_course
+	ORDER BY lesson_id;
+	
\ No newline at end of file